Pneumatic percussion device

ABSTRACT

In a pneumatically operated percussion device, a working cylinder with a differential-type piston reciprocable therein is in constant communication with a compressed-air reservoir to cause the driving stroke. The piston is cup-shaped with an open lower end and has a cylindrical sleeve for engaging an annular chamber in the working cylinder. The bottom wall of the cylinder has an outlet for venting air from the cylinder to the atmosphere during the driving stroke. In the initial position of the piston, the annular chamber communicates with an air supply line, and during the driving stroke of the piston the annular chamber is vented. At the completion of the driving stroke a venting valve in the piston is opened, and air from the supply line is admitted to the annular chamber to return the piston to its initial position.

United States Patent 1721 lnvcnwr Lanes, Wilfried 3,147,670 9/1964Spencer 92/108 1 Bmkhold, 3101 Altenhagemccrmany 3,361,036 1/1968 Harveyet a1... 91 224 1 1 pp N9 11,684 3,479,926 11/1969 11111161 91/404 I 1Flled Feb-16,1970 3,512,454 5/1970 Perkins 91/461 [45] Patented Jan. 11,1972 [32] Priority 18 1969 Primary Exarnmer-Paul E. Maslousky [33]Germany Attorney-H1bben, Noyes & Blcknell [31] P1908085.4

ABSTRACT: In a pneumatically operated percussion device, [54] PNEUMATICPERCUSSON DEVICE a working cylinder with a differential-type pistonreciprocabl e 7 Claims, 2 Drawing Figs there1n 1s in constantcommunlcanon w1th a compressed-an reservoir to cause the dr1v1ng stroke.The plston 1s cup-shaped [52] US. Cl 91/401, with an open lower end andhas a Cylindrical Sleeve for engag 91/4 R1 91/446- 92/108 ing an annularchamber in the working cylinder. The bottom [51] Int. Cl ..F15b 15/22, nf the cylinder has an outlet f venting f the Fl5b 5/17 cylinder to theatmosphere during the driving stroke. in the in- [50] Fleld ofsearch91/40], 1 position of the piston the annular chamber commu 4041 4611 417R1 417 A; 92/108 nicates with an air supply line, and during the drivingstroke of References Cited the plston the annular chamber 1s vented. Atthe completion of the drlvmg stroke a ventmg valve in the piston 15opened, UNITED STATES PATENTS and air from the supply line is admittedto the annular 2,664,859 1/1954 Green 92/108 chamber to return thepiston to its initial position. 2,960,067 11/1960 Osborne 91/417 A 1 l fi i 2 g-3s aof y 34 v l 3 1 I] 5 9 1 i as 398 10 l I 25 r 1 J l 1 11 4 I7 1 27/ 22 20 I" l 1 I if 1 n 6 l1 2a 37 4o 36 23 I 1 PNEUMATICPERCUSSION DEVICE DESCRIPTION The present invention relates to apneumatically operated percussion device especially to a portablestapling device for driving fastening means such as staples and the likeinto a workpiece by means of a driver which is actuated by a pistonoperated by compressed air. The piston is returned to its initialposition by pneumatic operation after completion of its driving stroke.

It is known in the art to store the air which is necessary for returningthe piston in an air chamber surrounding the work ing cylinder. Thischamber receives the air displaced by the piston during its drivingstroke and additional compressed air from an air reservoir. During thedriving stroke of the piston the interior of the working cylinderbeneath the piston must be vented to the atmosphere to avoidcounterpressure in the cylinder during the driving stroke. By suchventing of the cylinder a large loss of compressed air is provokedwhereby the efficiency of the percussion device is considerably reduced.The air storage chamber and the usual air inlet valve of the workingcylinder are expensive. Further, they increase the weight of the deviceand make its manipulation difficult.

It is an important object of the present invention to provide apneumatically operated percussion device in which the consumption ofcompressed air is reduced in comparison to the prior art devices.

Another object of the invention is the provision of a pneumatic staplerof smaller dimensions and of lower weight, than hitherto.

A further object is to provide a pneumatic fastener device whicheliminates the intake valve for the admission of com pressed air to theworking cylinder.

These and other objects and features will become apparent from thefollowing description in connection with the accompanying drawings inwhich by way of an example a portable pneumatic fastener implement isrepresented as a preferred embodiment of the invention. In the drawings:

'. FIG. 1 is a cross-sectional view of the fastener tool embodying thisinvention with the parts in their initial position; and

FIG. 2 is the same sectional view with parts in position aftercompletion of a driving stroke.

The device of the present invention is characterized by the opencommunication of the upper terminal portion of the working cylinder witha compressed-air reservoir without the use of an intake valve and by theprovision of means for admitting compressed air from an air supply lineto said compressed-air reservoir.

Preferably the piston is of the differential or stepped type and cupshaped, the upper portion of which has a smaller diameter and defines anannular shoulder and the lower portion of which comprises a cylindricalsleeve slidable in and guided in an annular chamber. Said chamber isenclosed by the working cylinder and the latter is surrounded by thecompressed-air reservoir. The compressed-air reservoir communicates viathe annular chamber and valve means with a compressed-air supply line aventing valve in the piston can connect the reservoir with theatmosphere.

Referring now to the drawings, the portable pneumatic stapler embodyingthe invention comprises a body casing 1 with a working cylinder withinwhich a piston 2 is slidably mounted. The piston 2 is cup shaped and ofthe differential type with an upper portion 29 of smaller diameter thanthe working cylinder 5. The lower portion 30 of piston 2 comprises asleeve which is sealed against the interior of the sidewall of theworking cylinder 5 by means of a resilient packing ring 31. The pistonportions 29 and 30 define an annular shoulder 13. A handle section ofthe body casing 1 encloses a compressed-air reservoir 4, which is inpermanently open connection with the upper end portion of the workingcylinder 5, as is best shown in FIG. 2 of the drawings. A tube wall 27is inserted in the working cylinder 5 and defines with its sidewall anannular chamber 3. The sleevelike lower piston portion 30 slides in thisannular chamber 3 and by means of a packing ring 32 is sealed againstthe external surface of the tube wall 27. A driver 2a is secured to theupper piston portion 29 and serves to drive staples from a magazine 33into a workpiece when the piston 2 performs its working stroke, as isconventional.

In the initial position of the piston 2, as is shown in FIG. 1, itsupper portion 29 engages a cylindrical recess 16 of the cover of thebody casing l and is sealed off by a packing ring 17 slidable on thecylindrical face of the recess 16. The upper piston portion 29 has anannular clearance 34 into which during the working stroke of the piston2 the tube wall 27 fits. A narrow bore or passage 15 of the upper pistonportion 29 connects the clearance 34 with the upper face of piston 2.The upper piston portion 29 further comprises an axial bore 35 which isclosed off at its upper end by a vent valve 14 secured to the upper endof a valve rod 140. This valve rod is longer than the axial length ofthe whole piston 2 whereby in its lower terminal position as shown inFIG. 2 the vent valve 14 is opened. When piston 2 performs its workingor return stroke or is in its initial position as shown in FIG. 1 thevent valve 14 is closed.

The bottom wall 36 of the working cylinder 5 is provided with an outletopening 23 for venting the air from the working cylinder 5 displaced bythe piston 2 during its working stroke to the atmosphere. This bottomwall 36 carries the flangeshaped lower end of the tube wall 27 and aresilient bumper 28 for limiting the downward travel of piston 2.Adjacent the bumper 28 a port 26 is arranged which communicates with adifferential piston valve 6 provided with an axial passage 6a andslidably mounted in a valve housing 37. Said valve housing 37 isprovided with an outlet opening 11 and communicates via a port 38 with acontrol valve 7 which comprises a valve stem 22 movable by a triggerlever 21. Valve stem 22 carries at its lower portion a vent valve 20which communicates via a clearance 40 of the lower end portion of valvestem 22 with the atmosphere. The control valve 7 via a port 39 and aspringloaded ball valve 8 communicates with an air admission chamber orpassage 10. A spring-loaded ball valve 9 connects the air admissionpassage 10 with the air reservoir 4 which via ports 18 in the sidewallof the working cylinder 5 communicates with the annular chamber 3. Saidports 18 are normally closed by a resilient ring 12 inserted in anannular groove 19 on the external surface of the sidewall of the workingcylinder 5. Ports I8 and ring 12 constitute a one-way or nonreturn valvebetween the annular chamber 3 and the air reservoir 4.

The operation of the stapling device is as follows: The initial positionof the driving mechanism is illustrated in FIG. 1. To drive a fasteningmeans into a workpiece, the operator will grasp the handle of the bodycasing I and squeeze the t igger lever 21 whereby the valve stem 22 ofthe control valve 7 is lifted into the position shown in FIG. 2, so asto close the port 39 and open the vent valve 20. The air within theannular chamber 3 through the port 26, and the outlet opening 11 of thedifferential piston valve 6, is permitted to escape to the atmosphere.The air in the compressed-air reservoir 4 acts on the annular shoulder13 of the piston 2, whereby piston 2 starts to descend. As soon aspiston 2 has moved from the cylindrical recess 16, the air from thereservoir 4 acts upon the whole upper face of the piston 2 and pressesit downward whereby the driver 2a separates a staple from the staplestrip in magazine 33 and drives it into the workpiece. The air displacedby the piston during its driving stroke escapes from the interior of theworking cylinder 5 through the outlet opening 23 to the atmosphere.

When the piston has terminated its downward stroke, it will abut thebumper 28. At the same time the rod 14a abuts the cylinder bottom wall36 and opens the vent valve 14 of the upper piston portion 29, as isshown in FIG. 2.

As the trigger lever 21 was squeezed only for a short time to theposition shown in FIG. 2 to start a working stroke and returns to itsinitial position as shown in FIG. I, also the control valve 7 and itsvalve stem 22 move downward, whereby the air in the compressed-airadmission passage 10 via the opened ball valve 8 flows through ports 39,38, valve housing 37, passage 6a and port 26 into the annular chamber 3.The air acting on the rear face 25 of the differential piston valve 6moves it to its terminal left-hand position as shown in FIG. 1, wherebythe outlet opening 11 is closed. The air flowing into the annularchamber 3 now returns the piston 2 to its initial or retracted position,as the valve rod 14a has closed its vent valve 14. The air from thecylindrical recess 16 displaced by the piston 2 at the end of its returnstroke escapes through the narrow passage 15, the clearance 34, theinterior of the working cylinder and the outlet opening 23 to theatmosphere.

In the upper terminal or initial position of piston 2 the compressed airfrom the air admission passage 10 flows through the valve assembly 8, 7,6, the port 26, the annular chamber 3, and the ports 18 into thereservoir 4 and replaces the air quantity which had been consumed by thepreceding working stroke. As the piston during its return stroke partlycompresses the air within the air reservoir 4, only a small quantity ofair under pressure flows from the annular chamber 3 through the ports 18into the reservoir 4 to produce here the primary air pressure, whichonly depends on the spring tension of the ball valve 9.

The present invention is of considerable advantage for pneumaticequipment of all kinds, and in particular for portable pneumaticstapling devices and on account of the limited consumption of air underpressure allows a high efiiciency.

As for the device embodying this invention the hitherto customary airintake valve is not necessary, a simple structure and a low weight areattained. This advantage is of particular importance for portabledevices for driving in staples, nails and other fasteners, themanipulation of which is made easier. The invention is also ofimportance for pliers and packing devices for stapling the lids ofcardboard boxes.

What] claim is:

1. In a pneumatically operated percussion device comprising a bodyportion containing a cylinder having a sidewall and a bottom wall at oneend thereof, a cup-shaped differentialtype piston in said cylinder, saidbody portion defining an air reservoir around said cylinder, said airreservoir being in permanent communication with the opposite end of saidcylinder, a tubular member in said cylinder carried by the bottom walland defining with said sidewall an annular air chamber, said pistonhaving an annular clearance for receiving said tubular member, an airadmission chamber, and valve means for ad mitting compressed air fromsaid air admission chamber to said annular air chamber and to said airreservoir.

2. The device of claim 1 wherein said cup-shaped differential-typepiston comprises a lower cylindrical sleeve, said sleeve being guidedwithin and sealed against said annular air chamber, said sidewall ofsaid cylinder having ports and check valve means closing said ports sothat said air reservoir may be filled from said annular air chamber.

3. The device of claim 1 wherein vent valve means is arranged in saiddifferential-type piston, said vent valve means having a valve rod whichat the end of the driving stroke of said piston abuts the cylinderbottom wall, whereby said vent valve means is opened to enable a returnof the piston.

4. The device of claim I wherein a valve assembly comprising a manuallyoperable control valve is mounted in a passage connecting said airadmission chamber with said annular air chamber.

5. The device of claim 1 wherein a spring-loaded ball valve is disposedbetween said air admission chamber and said air reservoir.

6. The device of claim 1 wherein a cover of said body portion comprisesa cylindrical recess for receiving said cupshaped differential-typepiston when in its initial retracted position.

7. The device of claim 6, wherein said piston is provided with a borefor venting the air from said cylindrical recess which is displaced bythe pistor; on its eturn stroke.

1. In a pneumatically operated percussion device comprising a bodyportion containing a cylinder having a sidewAll and a bottom wall at oneend thereof, a cup-shaped differential-type piston in said cylinder,said body portion defining an air reservoir around said cylinder, saidair reservoir being in permanent communication with the opposite end ofsaid cylinder, a tubular member in said cylinder carried by the bottomwall and defining with said sidewall an annular air chamber, said pistonhaving an annular clearance for receiving said tubular member, an airadmission chamber, and valve means for admitting compressed air fromsaid air admission chamber to said annular air chamber and to said airreservoir.
 2. The device of claim 1 wherein said cup-shapeddifferential-type piston comprises a lower cylindrical sleeve, saidsleeve being guided within and sealed against said annular air chamber,said sidewall of said cylinder having ports and check valve meansclosing said ports so that said air reservoir may be filled from saidannular air chamber.
 3. The device of claim 1 wherein vent valve meansis arranged in said differential-type piston, said vent valve meanshaving a valve rod which at the end of the driving stroke of said pistonabuts the cylinder bottom wall, whereby said vent valve means is openedto enable a return of the piston.
 4. The device of claim 1 wherein avalve assembly comprising a manually operable control valve is mountedin a passage connecting said air admission chamber with said annular airchamber.
 5. The device of claim 1 wherein a spring-loaded ball valve isdisposed between said air admission chamber and said air reservoir. 6.The device of claim 1 wherein a cover of said body portion comprises acylindrical recess for receiving said cup-shaped differential-typepiston when in its initial retracted position.
 7. The device of claim 6,wherein said piston is provided with a bore for venting the air fromsaid cylindrical recess which is displaced by the piston on its returnstroke.